1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to networking devices and transmission of content using them. More particularly, the present invention relates to a networking device and a data transmitting method using the same, capable of securing better quality of service when transmitting content over the network.
2. Description of the Related Art
As multimedia services are increasingly in need, criteria for securing better quality of service (QoS) when the multimedia content have been defined. Since any service not meeting the criteria cannot be properly supplied, research to establish accurate specifications and support them by a variety of protocol layers has been actively conducted.
For example, lower-level protocols such as a fiber distributed data interface (FDDI) and an asynchronous transfer mode (ATM) secure processing data within the maximum delay time, provide reservation functions of resources for the secured throughput, and define a variety of QoS parameters of a signal protocol.
Further, to prevent the quality of audio or video from deteriorating when transmitting multimedia data in a stream, QoS parameters including the maximum size of the transmitted data unit, and throughput are defined.
To use a limited bandwidth in an optimal manner, an application layer protocol divides multimedia data into several streams and each divided stream has a different QoS.
FIG. 1 illustrates a conventional coordination of QoS on the Internet.
As illustrated, a user transmits content to requesting information of a service supplied by a server 20 through a client 10 and information on QoS of the requested content (S11).
At this time, the user determines the QoS information based on various quality conditions relative to the content of the requested service.
QoS information is composed of content types, and quality criteria and classifications for those quality criteria.
For example, when the content type is image, the two quality criteria are color and size.
Examples of quality classifications include Full Color, Reduced Color, or Black and White for the color criterion, and Original, Small, or User Specified (size & scale) for the size criterion.
Table 1 shows quality criteria and classifications for the image, video and audio content types.
TABLE 1Content Quality Criteria & ClassificationsTypeQuality CriteriaQuality ClassificationsImageColorFull Color/Reduced Color/Black and WhiteSizeOriginal/Small/User Specified (size & scale)VideoFrame rate>25FPS/>12FPS/>5FPSResolution720 × 576/352 × 288/176 × 144AudioQualityTelephone/Hi-Fi Stereo/Others
The server 20 determines whether it can supply the content, and it transmits the QoS information and the requested content to the client 10 if it can (S12).
The content transmitting method through QoS coordination (as described above) will be described with reference to FIG. 2, which illustrates a method for requesting content through QoS coordination according to the conventional art.
As illustrated, the user selects a content to be requested, of a service supplied from the server 20 through the client 10 (S21), and determines QoS information on the selected content (S22).
At this time, the user determines the QoS information as desired (see the quality conditions shown in Table 1).
The client 10 transmits content requesting information and QoS information to the server 20 (S23), and the server 20 determines whether it can supply the content with that QoS (S24).
When it is determined that it can transmit the content with the desired QoS, the server 20 transmits the content with the desired QoS (S25).
However, when it is determined that the QoS is out of its available range, the server 20 coordinates the transmitted QoS information with the QoS that it can supply (S26).
Then, the server 20 transmits the coordinated QoS information and the requested content to the client 10 (S27).
The server compares the bandwidth requirements of the QoS with the bandwidth of the network, and coordinates the QoS.
In other words, since the QoS degrades when the required bandwidth is larger than that of the network, the server determines whether the network bandwidth is suitable for the content to be transmitted according to the coordinated QoS, and re-coordinates the coordinated QoS according to the result of the determination.
As illustrated in FIG. 3, in the method of re-coordinating the QoS according to a state of the network, the bandwidth of the coordinated QoS is compared with that of the network (S31).
As a result of the comparison, when the bandwidth of the coordinated QoS is smaller than the network bandwidth, the server 20 transmits the content according to the coordinated QoS (S32).
When the bandwidth of the coordinated QoS is larger than the network bandwidth, the server 20 re-coordinates the coordinated QoS according to the network bandwidth (S33), and transmits the content based on the re-coordinated QoS (S34).
The above-described service transmitting method through the QoS coordination on the Internet according to the conventional art can not be properly applied to an environment under which a multiplicity of servers and clients, such as home network are in existence.
In other words, the Internet is a fixed network environment whereas a home network is not. In a home network, devices that instantaneously constitute a separate network exist and then disappear after having performed their function. As such, there it is difficult to coordinate the service bandwidth due to the uncertainty of the network.
Under the circumstances, a method is needed to secure a stable QoS in wired and wireless networks as well as on the Internet.
Korean Patent No. 0150282 discloses a method of preferentially designating the service quality of a multimedia service according to the state of the network to which an Internet client is connected, and controlling the service quality of multimedia data on the World Wide Web (WWW). However, a temporary slow-down is caused when multiple users share a resource. However, this method cannot be applied to those cases where multiple servers and clients exist and have dynamic network connections, as in a home network.